Electron beams with helical wavefronts carrying orbital angular momentum are expected to provide new capabilities for electron microscopy and other applications. We used nanofabricated diffraction holograms in an electron microscope to produce multiple electron vortex beams with well-defined topological charge. Beams carrying quantized amounts of orbital angular momentum (up to 100ℏ) per electron were observed. We describe how the electrons can exhibit such orbital motion in free space in the absence of any confining potential or external field, and discuss how these beams can be applied to improved electron microscopy of magnetic and biological specimens.

The present invention relates to a device capable of producing a high resolution chemical analysis of a sample, such as fluid, based upon nuclear magnetic resonance (NMR) spectroscopy, where the nuclear magnetic polarizations of the sample are generated by sequentially illuminating the sample with a focused beam of light carrying angular orbital angular momentum (OAM) and possibly momentum (spin). Unlike in usual NMR used for magnetic nuclear resonance imaging (MRI) or spectroscopy, the invention does not make use of a strong magnet.

Orbital angular momentum (OAM) of a helical beam is of great interests in the high density optical communication due to its infinite number of eigen-states. In this paper, an experimental setup is realized to the information encoding and decoding on the OAM eigen-states. A hologram designed by the iterative method is used to generate the helical beams, and a Michelson interferometer with two Porro prisms is used for the superposition of two helical beams. The experimental results of the collinear superposition of helical beams and their OAM eigen-states detection are presented.

About this Blog

I believe that OAM may have some unique applications in RF signaling especially for new multi-spectral coding techniques, search for SETI and in the remote detection of bombs, land mines and IEDs.

By combining RF OAM with Nuclear Quadrapole Resonance (NQR) it may be possible to overcome many of the limitations of NQR at the moment for detecting explosives. NQR produces a very weak signal that happens to be in the RF bands of commercial broadcasting. So remote (or even close proximity detection) is a real challenge. The attraction of OAM is the possibility of detecting NQR response to OAM modulated signals at a distance through spatial filtering of the response signal to elminiate common RF interference. Also OAM appears to have no limit to "modulation" power i.e the OAM can be made powerful enough to even create physical resonance as for example the "optical spammer" noted in some of the OAM research. Other resonance stimulation may be possible such as rapidly changing the direction and polarity of the OAM. "Pumping" the NQR sensitive molecules into higher circular vibrational modes with OAM resonance can also be used to enable a secondary OAM RF signal to absorbed, emitted or cross modulated in the detection process. The use of such techniques might enable to detection of explosives at a distance and conceivably even be used to disable explosive devices. This includes atomic bombs which need to use a conventional explosive to ignite the fission core.

An excellent overview of OAM can be found at:http://www.physics.irfu.se/Publications/Presentations/ThideEtBergman%3ACSC_SETI%3A2008.pdf

About Me

Bill St. Arnaud is a consultant and research engineer who works with clients around the world on a variety of subjects such as next generation Internet networks and developing practical solutions to reduce CO2 emissions such as free broadband and dynamic charging of eVehicles. He is an author of many papers and articles on these topics and is a frequent guest speaker. For more details on my research interests see https://www.researchgate.net/profile/Bill_Arnaud